1. Field of the Invention
The present invention relates to a label printing and applying device, principally of the portable type (which will be referred to as a "hand labeler"), and more particularly to a constant pressure printing mechanism for use in the hand labeler.
2. Description of the Prior Art
Most conventional hand labelers have an actuating lever, which is comprised of an integral hand lever and printing lever. The actuating lever is pivotally supported on a pivot pin which is positioned between the hand lever and the printing lever. A printing head is mounted to the leading end of the printing lever for being moved toward a printing platen together with the printing lever by squeezing of the hand lever.
Since the squeezing force that is applied to the hand lever of a conventional hand labeler is converted directly into printing pressure against the platen, varying squeezing forces on each imprinting are liable to produce different shadings of the imprints. If the hand lever is squeezed especially strongly and swiftly, the impact of the printing head against the platen causes the printing head to slightly bounce upon the platen which may cause double printing of the labels.
Even unclearly printed labels obtained with conventional hand labelers are considered to minimally succeed in performing their functions even if they only can be barely read out both by customers, when they purchase commodities, and by sales clerks or cashiers when they calculate the sales. In recent years, however, clerks and cashiers at check-out registers are being replaced by optical character readers which are connected with an electronic computer system. This is part of a POS (i.e., Point-of-Sale) system, in which the numerals or characters (e.g., bar codes or OCR symbols) on the labels are automatically read out, for recording and processing in the computer system, business information about each commodity, such as the stock, sales, sales analysis and profit calculation. In a POS system, the imprints on the labels must be clear at all times.